What's the difference between heterophony and homophony?

Heterophony

Definition:

• (n.) An abnormal state of the voice.

Example Sentences:

Homophony

Definition:

• (n.) Sameness of sound.
• (n.) Sameness of sound; unison.
• (n.) Plain harmony, as opposed to polyphony. See Homophonous.

Example Sentences:

• (1) The difference between word and nonword processing was shown by manipulations of the visual similarity and the homophony between stimuli presented successively.
• (2) Visual similarity affected both words and nonwords, whereas homophony affected words only.